This invention relates to sensors or switches which utilize the fact that gravity will maintain an unrestricted conductive contact element, such as a metal ball or a ball of liquid mercury or other electrically conductive liquid, in the lowermost position relative to its containment chamber to indicate attitudinal position of the switch or sensor relative to true vertical, and correspondingly the attitudinal position of any object attached thereto. More particularly, the invention is a sensor which is able to monitor the attitudinal position of an object relative to true vertical over a three axis pathway, such that a single sensor can monitor the movement over the pathway even if the object and sensor are inverted or tilted in any plane, and regardless of whether the object is fixed in space or moved positionally.
There are many situations where it is necessary or desired to monitor or sense the attitudinal position of an object relative to true vertical. Switches or sensors which utilize the effect of gravity on a ball of liquid mercury or an electrically conductive metal ball or roller are well known, the switch being designed such that the unrestricted conductive member makes or loses contact with a pair of leads in an electrical circuit dependent on the attitude of the switch relative to true horizontal, such that either contact with the leads or loss of contact with the leads which occurs when the attitudinal position of the switch is altered relative to vertical results in a signal or other electrical action occurring. Such switches or sensors are commonly referred to as mercury or gravity switches. Such simple gravity switches work when the object or switch is tilted or rotated about a non-vertical line, such that the switch is activated or deactivated when a particular angle relative to vertical is exceeded and gravity causes movement of the conducting ball away from or against the contact leads. In order to track attitudinal positioning of an object along various curved pathways in the orthogonal X-Y-Z three axis world, where the switch is rotated, tilted and/or inverted, the known solution is to attempt to combine a number of such two dimensional switches, with the switches oriented in opposing directions. Any such solution, especially when the object is inverted, requires determination of sequential activation and deactivation scenarios, since certain of the switches will be non-functional or provide incorrect signals when the object passes through various positions relative to vertical.
It is an object of this invention to provide a single gravity-type sensor switch which monitors the position of an object over a three dimensional pathway which extends dimensionally about all three orthogonal axes where the object may be tilted, rotated or inverted, as well as translated through space rather than maintained at a fixed location, so as to provide a signal to indicate that the object is moving in the correct three dimensional manner. It is a further object to provide such a switch which contains a gravity controlled contact member which remains at the bottom of the sensor because of gravity as the position of the sensor changes relative to true vertical, where the sensor comprises a curved contact pathway corresponding to the desired three dimensional movement path of the object, where the contact member is contained within a curved tube, in particular a 360 degree torus having a circular transverse cross-section, or a pair of matching curved surfaces which can be part or all of a sphere, a combination of multiple curved surfaces or of any three dimensional curvilinear pathway in space. It is a further object to provide such a switch where the gravity responsive member is composed of a conductive liquid ball or bead immersed in a carrier liquid, where the material comprising the conductive liquid ball is immiscible in the liquid carrier. It is a further object to provide such a switch where the switch operates by sensing the difference in resistivity between the conductive liquid ball and the carrier liquid.
The invention is a gravity-type sensor switch where a gravity responsive member remains in the lowermost portion of a retaining chamber as the switch is moved through space. The gravity responsive member, which may be a ball of liquid mercury or other conductive liquid, an electrically conductive solid metal ball or roller, or similar type object, is retained within a defined curvilinear chamber having at least one conductive pathway mounted along one of the walls of the chamber which allows for relative movement between the gravity responsive member and the pathway as the attitudinal position of the switch relative to true vertical changes, true vertical being defined as the line passing through the switch and the gravitational center of the earth. A sensing pathway is formed along the curved walls such that a completed electrical circuit is produced when the sensing pathway is moved to be in contact with the gravity responsive member. The sensing pathway may comprise a number of discrete contact points or lead pairs positioned along the pathway, or it may comprise a pair of continuous conductive strips or wires, either embedded on the surface of the walls or disposed into the interior of the chamber, or it may comprise a single set of contact points, a wire or a strip in combination with a conductive surface on the curved wall of the chamber, or may comprise a conductive surface coating applied to one or both of opposing surfaces or chamber walls. The chamber walls may comprise the interior wall of a curved tube, such as a 360 degree torus having a circular transverse cross-section, or a pair of curvilinear, equidistantly spaced walls having matching surfaces, or a hemisphere or a spherical surface. The wall pairs may comprise a sphere within a sphere, a section of a sphere within a sphere, or any configuration of paired curvilinear walls. The curved tube may comprise a portion of a circle or may be spiraled or curved in multiple curves of differing radii.
The sensing pathway occupies at least two orthogonal dimensions and enables the sensor to function regardless of tilt, rotation or inversion. The particular sensing pathway is determined by the desired positional movement of the object to be monitored. The zero position, defined to be the position of the gravity responsive member relative to the remaining components of the sensor at any moment in the movement path of the object, i.e., the lowest possible position for the gravity responsive member within the retaining walls for a given attitudinal position, is determined for the object""s entire movement pathway. With this information, the proper sensing pathway can be constructed on the chamber walls so that as the object is moved through three dimensions, the sensor pathway will be repositioned relative to the gravity responsive member, which has a fixed spatial attitude due to gravity. As long as the object is moved in the correct pathway, the gravity responsive member will remain in contact with the sensing pathway and the electrical circuit will be maintained. If the object is moved out of the predetermined pathway, the gravity responsive member will not remain in contact with the sensing pathway and the circuit will be broken. Alternatively, the sensor can be designed such that movement in the proper pathway results in no contact with the contacting element, with the sensing pathways arranged to provide a complete circuit only when the object is incorrectly moved. The presence or absence of an electrical circuit is used to provide a signal or indication, or can be used to actuate other electrical devices to effect desired results. The switch may also be constructed using optical components such as a combination of photosensors and defined light sources, receivers and emitters, whereby the gravity responsive element becomes an opaque blocking element between the light sources and the photosensors when properly positioned.
In a preferred embodiment, the switch is constructed with the gravity responsive member being an electrically conductive liquid ball or bead disposed within a non-conductive carrier liquid, the conductive liquid ball and the carrier liquid being immiscible such that the conductive liquid ball maintains a spherical or relatively spherical configuration, and where the conductive liquid ball is of greater density or specific gravity than the carrier liquid, such that the conductive liquid remains at the bottom of the liquid carrier. For example, the conductive liquid bead may be composed of ethylene or propylene glycol, with the carrier liquid being a silicone oil. Rather than providing a completed circuit, a switch utilizing a liquid ball gravity responsive member in a carrier liquid may be provided with circuitry to sense the difference in resistivity of the gravity responsive member versus the carrier liquid, with the result determining if the switch creates an open or closed operational circuit.